1. Field of the Invention
The present invention generally relates to hermetic cooling compressors and, more specifically, to fastening a compression valve onto a valve plate arranged in the yoke of a compressor, and a method of operating such a compression valve.
2. Description of Related Art
Hermetic cooling compressors are composed of a compressor unit and an electric motor which are disposed within a hermetically sealed casing. The compressor unit is formed by a main body supporting a crankshaft. The crankshaft is rotatably powered by the electric motor. The main body contains a hollow cylinder through which the piston reciprocally travels, compressing the cooling gas. A valve plate and yoke assembly are mounted at one end of the cylinder. Proper functioning of the valves and ducts through which the aspirated and compressed gases pass is very important since, to a great extent, the results of the compressor depend on these valves and ducts to supply a satisfactory level of energetic efficiency and a low level of noise. High energy efficiency and low noise are essential features in hermetic compressors, since it reflects advantageously in the operational cost of the compressor, which is used in high production volume appliances.
There are various known solutions that attempt to meet, more or less satisfactorily, the aforementioned operating requirements. U.S. Pat. No. 4,723,896 and EP 582,712 are exemplary of the art. Both of these publications disclose valve assembly plates similar to those described above. However, in the valve assembly plates described in these patents, the levels of efficiency and/or noise emission, as well as the simplicity of design do not meet those achieved by the present invention.
The energy efficiency of hermetic compressors is partially determined by the response time for opening the compression valve. The compression valve response time depends, partially, on the type of valve mounting employed. It is known to use preloaded compression valves having a force normally directed toward the closing surface of the compression duct provided by the mounting system itself. When the piston, in its reciprocating motion, begins the compression stroke, the compression valve remains closed for a short time until the pressure inside the cylinder has balanced the pressure in the yoke plus the preloaded force of the valve. The displacement (x-axis) versus compression force (y-axis) is shown graphically in FIG. 1 (preloaded valve) and FIG. 2 (valve not preloaded).
One of the causes of noise in this type of compressor is related to opening and closing impact of the compression valve. The noise thus generated by the valve is transmitted as sound waves through the air and also structurally through components in direct contact with the valve assembly and radiate to the exterior through the casing of the compressor.
The compression/damper valve assembly in the abovenoted patents is mounted by means of a system of yokes possessing at least two elements. One of the elements serves as a bumper or stop for the valve and the other as a mounting element. The solution proposed in the aforementioned patents, therefore, requires the manufacture of at least two parts, which is economically undesirable.
Accordingly, there exits a need in the art for an economical and quiet valve plate for a hermetic compressor.